On the advanced search form, you will see a section like "Search by Page Type"
If you select "Any" (the default) it will show you results of all types. If you select "Page" by itself, it should show you pages that don't also count as something else - so it will only show you templates if you select "Templates"
However, I see on the wiki's sidebar search box that "Template" is not available as one of the filter choices. In this case, selecting "Page" in the sidebar probably shows templates in the drop-down too (but pressing enter returns search results that do not include templates). If anything, this is a jarring inconsistency; I will look into it.